Device for electrically heating a vertically erect chamber

ABSTRACT

A device for electrically heating a vertically erect chamber comprising several heating zones arranged vertically one above the other. The components of the device, with the exception of the insulating components, are made from graphite materials. Each zone (Z) comprises a number of supports ( 1 ), arranged in an essentially even distribution around the chamber for heating, which simultaneously serve as electrical supplies for the heater, and the heater for each zone (Z) is fixed at one end and longitudinally displaceable at the other end.

FIELD OF THE INVENTION

The invention relates to a device for electrically heating a verticallyerect chamber, for example a reactor, to high temperatures (≧1000° C.)and/or with high power (30 to 1000 kW per zone), comprising severalheating zones arranged vertically one above the other and wherein thecomponents of the device, with the exception of the insulatingcomponents, are made from graphite materials.

BACKGROUND OF THE INVENTION

High-temperature heatings made from graphite materials must be operatedin a gasproof, air-free heating zone. The electrical supplies must beconducted through the wall of a dense and comparatively cold case.

Two-zone graphite heatings that are arranged one above each other, forvertically erect (reaction) chambers, can be arranged directly on top ofeach other separated from each other by insulating components. Theelectrical supplies of a heating zone, however, must be able to balanceout the difference in length of the heater compared to the case causedby different thermal expansibility.

From the third heating zone on, however, the electrical supplies of thecentral heating zones must be conducted radially out of the heatingzone. These can now be conducted radially and flexibly (by means ofcooled metallic materials) through the side wall of the case or withlarge-design graphite electrical supplies outside the heating verticallyupward or downward which, however, requires flexible, metallicconnections. Particularly in the case of very big heaters (e.g. up to 10m height) lateral connection causes great problems during assembly.

In the case of large-design high-power heaters which are often operatedat low voltage (with the consequence of even bigger-andheavier-dimensioned parts) the electrical supplies of the heating zonesthat are arranged one above the other are very heavy and the wholeconstruction becomes mechanically more and more unstable the higher theconstruction is and high Carbon Fiber Composite (CFC) heating elementscan no longer carry the weight of the above heating zones with theirelectrical supplies. Therefore subframes become necessary for theindividual heating zones comprising separate supports resting outsidethe heating.

SUMMARY AND OBJECTS OF THE INVENTION

The object of the invention is therefore to further embody and developthe initially mentioned device for electrically heating a verticallyerect chamber such that the largest possible degree of stability andfunctional capability for the whole device is achieved with lowconstructional complexity.

This object is achieved in a device for electrically heating avertically erect chamber to a high temperature and with high power,comprising several heating zones arranged vertically one above the otherand each being provided with an electrical supply, in that each zone issurrounded by a plurality (twice or in the case of a three-phraseheating 3 times the number of zones) of supports 1, arranged in anessentially even distribution around the chamber R for heating and theheaters, consisting of heating elements 6 and heating element connectors7, wherein 2 or 3 of such supports simultaneously serve as electricalsupplies for the heaters of each zone Z, and wherein the heaters foreach zone Z are arranged such as to be fixed ax one end thereof andlongitudinally displaceable at the other end thereof.

The inventive construction of such a tall, high (up to approx. 10meters), multi-zone (Z≧2) high-power heater made from graphite materialsprovides the following advantages:

-   -   the use of the supports of the subframe as electrical supplies,    -   the possibility of a vertically erect heating construction        without electrical supplies that need to vary in length,    -   the extension of the heating elements of the individual heating        zones without affecting the other zones,    -   the possibility to pre-assemble the individual heating zones and        to arrange them one above the other during final assembly.

A further teaching of the invention provides that the heaters arelongitudinally displaced by means of the guide pins 11 that are locatedon the surface opposite of the electrical supplies (joining elements 8or 9) of the heaters. This ensures that the heating elements 6 canexpand within their respective zone irrespective of the surroundingsubframe.

According to another embodiment of the invention the sole plates 4 ofeach zone are connected electrically conductive to the supports 1 by thejoining elements 2 and they are connected electrically insulating to thesupports 1 by the joining elements 3, whereby each sole plate 4 ispartitioned in two or three (in case of a three-phase heating)electrically separate areas.

A precondition to the construction of the heating according to theinvention is that the electrical supplies of the heaters of theindividual heating zones are located on the same level (on top or nearthe bottom). This can be achieved by at least three arrangements of theheating elements 6: By means of a 1-phase heating (2 electrical supplypoints) of 2n (n≧1) serially connected groups of i (i≧1 (with i=1: allin series)) parallel-connected heating elements or as a meander of onepiece or as a three-phase heating (3 electrical supply points) in radialconnection (electrical supply points are located on one level and theconnections of the 3 heating element groups (also groups of i parallelconnected heating elements) are located on the second level (for examplesupply points near the bottom and joining elements on top) or triangleconnection, where the three heating resistors consist of 2n (n≧1)serially connected groups of i (i≧1 (with i=1: all in series)) parallelconnected heating elements.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of the device according to theinvention in vertical cross-section; and

FIG. 2 is a schematic illustration of the device according to theinvention in horizontal projection (the lower level of a heating zone).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The illustrated embodiment depicts the basic structure of a device forelectrically heating a vertically erect chamber by means of a 5-zone1-phase heating, comprising vertically erect heaters with four seriallyconnected groups of heating elements (n=2) of four parallel connectedheating elements each (i=4) (for reason of transparency the joiningelements (one near the bottom and two on top) between the groups ofheating elements are omitted in FIGS. 1 and 2). The heating elements 6of the heaters (total number of 2n times i heating elements 6, theappropriate 2n times 2 heating element connectors 7 and the 2n−1 joiningelements of the groups of heating elements) are displayed as CFC stripsin the illustration, it is also possible, however, to use for exampleheating rods or heating tubes. CFC heating elements with a large surfaceare preferred for example where the power density and/or the temperatureon the heating elements must be restricted.

As the 10 electrical supplies of the 5 heating zones are simultaneouslyused as supports each of them is lead up to the upper end of the fifthheating zone independent of the actual installation height of therespective heating zone. Each of the supports 1 consists of sectionswhich are mechanically and electrically connected with each other bymeans of the joining elements 2 or 3. The height of a support 1 and ajoining element 2 or 3 determine the height of a heating zone Z.

A ring-shaped sole plate 4 is attached to the 10 joining elements 2 and3 of each level. Located on top of such sole plates 4 are the heaters ofeach heating zone, e.g. the heating elements 6 and their heating elementconnectors 7. The heaters for each heating zone are fixed at one end tothe sole plate 4 on which they are located on by means of joiningelements 8 and 9. The ring-shaped sole plates 4 are divided in twoelectrically insulated semi-rings 4A and 4B by means of electricallynonconductive insulating components 12. It is divided in a way such thatthe semi-rings are connected to each other with one joining element 2electrically conductive and with four joining elements 3 electricallyinsulating (by insulation ring 5).

The four heating element connectors 7 of the heaters stand upon thesemi-rings 4A and 4B of the sole plates by means of conductive andinsulating joining elements 9 and 8. The sole-plate semi-rings 4A areconnected electrically conductive with the first, sole-plate semi-rings4B with the last heating element connectors 7 (by means of conductivejoining elements 9) and with the two central heating element connectors7 electrically insulating (by means of nonconductive joining elements8). The heating element connectors 7 are connected with other joiningelements (not displayed in the drawing) such that a serial connection isestablished with the groups of heating elements (with i=4 heatingelements) formed by the heating element connectors 7.

At the upper end the heaters with their four heating element connectors7 are guided in insulating guide pins 11 that are attached to or in thesole plate 4 of the heating zone Z located above. The heaters arelongitudinally displaceable at their upper ends by the guide pins 11.This ensures that the heaters can expand within their respective zoneirrespective of the surrounding subframe.

The length of the supports 1 is dimensioned such that a sufficientexpansion gap 10 is formed. This allows to compensate the differentthermal expansibility of the supports 1 and the heaters withoutaffecting the other heating zones and/or the whole construction.

The five identically designed heating zones Z (which can however bevaried, for example to adapt the heating performance of the heatingelements 6 of the heaters) are put one above the other in a way that thesole plates 4 are each rotated by 72° (360°/5) connecting each of theheating zones Z with two other supports 1 electrically conductive. Tocomplete the upper-most heating zone another set (in the depictedembodiment 10 pieces) of nonconductive joining elements 3 and a soleplate 4 must be put on top.

The lowermost heating zone of the whole heating which is electricallyand thermally decoupled by the insulating components 14, rests on theshorter supports 13 (analogous to supports 1) on the sole plate 15 ofthe whole construction. For power supply the supports 13 can now beconducted directly through the sole plate 15 or can be rigidly connectedby separate power connections (both not displayed in the drawing).

In the displayed and in so far preferred embodiment the heating elements6 are arranged vertically erect. However, a suspended arrangement isalso possible, in that the electrical supplies with the joining elements8 and 9 would be arranged in the upper area and the expansion gap 10near the bottom.

Other designs of the heating elements 6, e.g. one-piece CFC meanders,may provide heating element connectors 7 and joining elements 8 and 9which are partly or completely combined in one piece.

The most different graphite materials can be used to construct theheating specified above. Because of the required high stability it willbe expedient, however, to make the sole plates 4 from CFC materials andthe joining elements 2 and 3 from isostatically pressed finest-corngraphites of highest solidity.

Depending on the intended use and temperature the insulatingconstruction parts are made for example from Al₂O₃, BN or AlN.

According to a further teaching of the invention the fit between thejoining elements 2 and/or 3 and the supports 1 is carried out conically.Such conical connection does not only ensure a very good electricalconnection and an easy construction, but is in general the preconditionfor putting the individual heating zones Z above each other, whichadvantageously should be pre-assembled. According to the invention, inorder to limit the radial forces occurring in a conical fit to an extentthat the joining elements 2 and 3 do not break (the solidities of thebest types of graphite are very low compared to metallic materials), theaxial forces are restricted by installing compressible packs 16(dimensioned according to the forces to be expected) made from expandedgraphite, e.g. “Sigraflex®” made by the company SGL Carbon between thejoining elements 2 and the supports 1 and 13. The angle of the conicalfit which needs to be machined very precisely should be dimensioned suchthat no automatic interlocking may occur any longer.

For practical reasons the pre-assembly of the individual heating zonesshould be carried out on an assembly platform, consisting of theproperly arranged upper parts of the 2n supports 13, on top of which thejoining elements 2 and 3 with their insulation rings 5, the sole plate 4with the guide pins 11 and the insulating components 12 and subsequentlythe supports 1 are mounted. The heating elements 6 with their heatingelement connectors 7 can then be assembled-on the sole plate 4 and thejoining elements 8 and 9. Other components such as e.g. thermoelementretainers and beam umbrellas (not displayed) can also be installed. Forthe assembly of the heaters appropriate templates can be stuck on thesupports 1. The pre-assembled heating zones Z can now be rotated by 72°and mounted on the heating zone located below using a divisibleauxiliary frame with a traverse part engaging below the joining elements2 and 3, so that the guide pins 11 are pushed into the correspondingholes in the heating element connectors 7 of the heating zone below.

1. A device for electrically heating a vertically erect chamber, to ahigh temperature and with high power, comprising several heating zonesarranged vertically one above the other and each being provided with anelectrical supply, characterized in that each zone comprises a number ofsupports arranged in an essentially even distribution around the chamberfor heating, said supports simultaneously serving as electrical suppliesfor heaters for each said zone, including heating elements and heatingelement connectors, and that the heater for each zone is fixed at oneend thereof and longitudinally displaceable at the other end thereof,wherein said heaters are longitudinally displaced by means of guide pinsthat are located opposite of the electrical supplies.
 2. A deviceaccording to claim 1, characterized in that the heaters for each zoneare arranged on a sole plate and that each sole plate is partitioned inat least one of two and three electrically separate areas.
 3. A deviceaccording to claim 2, characterized in that the sole plates areelectrically connected to all supports in one level by means of joiningelements.
 4. A device according to claim 1, characterized in that thejoining elements connect two supports at a time that are arranged oneabove the other.
 5. A device according to claim 3, characterized in thatthe joining elements and the ends of the supports are provided with aconical fit.
 6. A device according to claim 5, characterized in that theangle of the conical fit is dimensioned such that no automaticinter-locking occurs.
 7. A device according to claim 3, characterized inthat compressible packs made from expanded graphite are provided torestrict the forces occurring between the joining elements and thesupports.
 8. A device according to claim 1, characterized in that thesupports are made from graphite material.
 9. A device according to claim2, characterized in that the sole plates are made from Carbon FiberComposite materials.
 10. A device according to claim 3, characterized inthat the joining elements are made from isostatically pressedfinest-corn graphites of highest solidity.
 11. A device according toclaim 1, characterized in that insulating construction parts are madefrom Al₂O₃, BN or AlN.
 12. A device according to claim 1, characterizedin that each zone comprises a pre-assembled unit comprising a sole platewith insulating components, joining elements with insulation rings,heating elements with heating element connectors, joining elements,guide pins and supports.
 13. A device for electrically heating avertically erect chamber, to a high temperature and with high power,comprising several heating zones arranged vertically one above the otherand each being provided with an electrical supply, characterized in thatthat each zone comprises a number of supports arranged in an essentiallyeven distribution around the chamber for heating, characterized in thatthat each zone comprises a number of supports arranged in an essentiallyeven distribution around the chamber for heating, said supportssimultaneously serving as electrical supplies for heaters for each zone,including heating elements and heating element connectors, and that theheater for each zone is fixed at one end thereof and longitudinallydisplaceable at the other end thereof, wherein said heaters for eachzone are arranged on a sole plate and each sole plate is partitioned inat least one of two and three electrically separate areas, wherein saidsole plates are electrically connected to all supports in one level bymeans of joining elements, wherein compressible packs made from expandedgraphite are provided to restrict the forces occurring between thejoining elements and the supports.
 14. A device according to claim 13,characterized in that the heaters are longitudinally displaced by meansof guide pins that are located opposite of the electrical supplies. 15.A device according to claim 13, characterized in that the joiningelements connect two supports at a time that are arranged one above theother.
 16. A device according to claim 13, characterized in that thejoining elements and the ends of the supports are provided with aconical fit.
 17. A device according to claim 16, characterized in thatthe angle of the conical fit is dimensioned such that no automaticinterlocking occurs.
 18. A device according to claim 13, characterizedin that the supports are made from graphite material.
 19. A deviceaccording to claim 13, characterized in that the sole plates are madefrom Carbon Fiber Composite materials.
 20. A device according to claim13, characterized in that the joining elements are made fromisostatically pressed finest-corn graphites of highest solidity.
 21. Adevice according to claim 13, characterized in that insulatingconstruction parts are made from Al2O3, BN or AlN.
 22. A deviceaccording to claim 13, characterized in that each zone comprises apre-assembled unit comprising a sole plate with insulating components,joining elements with insulation rings, heating elements with heatingelement connectors,joining elements, guide pins, and supports.
 23. Adevice for electrically heating a vertically erect chamber, to a hightemperature and with high power, comprising several heating zonesarranged vertically one above the other and each being provided with anelectrical supply, characterized in that that each zone comprises anumber of supports arranged in an essentially even distribution aroundthe chamber for heating, characterized in that that each zone comprisesa number of supports arranged in an essentially even distribution aroundthe chamber for heating, said supports simultaneously serving aselectrical supplies for heaters for each zone, including of heatingelements and heating element connectors, and that the heater for eachzone is fixed at one end thereof and longitudinally displaceable at theother end thereof wherein each zone comprises a pro-assembled unitcomprising a sole plate with insulating components, joining elementswith insulation rings, heating elements with heating element connectors,joining elements, guide pins, and supports.
 24. A device according toclaim 23, characterized in that the heaters are longitudinally displacedby means of guide pins that are located opposite of the electricalsupplies.
 25. A device according to claim 23, characterized in that theheaters of each zone are arranged on a sole plate and that each soleplate is partitioned in at least one of two and three electricallyseparate areas.
 26. A device according to claim 23, characterized inthat the sole plates are electrically connected to all supports in onelevel by means of joining elements.
 27. A device according to claim 23,characterized in that the joining elements connect two supports at atime that are arranged one above the other.
 28. A device according toclaim 23, characterized in that the joining elements and the ends of thesupports are provided with a conical fit.
 29. A device according toclaim 28, characterized in that the angle of the conical fit isdimensioned such that no automatic interlocking occurs.
 30. A deviceaccording to claim 23, characterized in that compressible packs madefrom expanded graphite are provided to restrict the forces occurringbetween the joining elements and the supports.
 31. A device according toclaim 23, characterized in that the supports are made from graphitematerial.
 32. A device according to claim 23, characterized in that thesole plates are made from Carbon Fiber Composite materials.
 33. A deviceaccording to claim 23, characterized in that the joining elements aremade from isostatically pressed finest-corn graphites of highestsolidity.
 34. A device according to claim 23, characterized in thatinsulating construction parts are made from Al2O3, BN or AlN.